What if a high end speaker measures really badly?

from what the graph shows, you have standing nodes. mainly cancelation - tall tale sign with those valleys.

if you were using them to record then you'd have problems with mix down.

but funny enough our brains do a lot of cognitive filtering such that much of it gets 'ignored'

if you were to test the speakers either outside, properly setup then you would get what the manufacture would get. Room acoustics is an important factor to good measurements, but not necessarily bad sound. Floor reflections are particularly  hard to control even in the studio. there are plenty of books on room acoustics and how to create a good environment. but its a good idea to provide some random reflection of random frequencies, such things as phase deflectors . but the most common and cost effective is floor to ceiling book shelves filled with various sizes of books. these will diffuse standing waves very effectively - you dont want to absorb the waves using dampening materials - unless you know what you are doing - REV is a free room analyzer that comes with a wealth of information  on room calibration.

I use it both in my studio and at home to calibrate my listening areas. 

Also should be aware on how the microphone used in testing is designed. omni's are great for overall response, but if you have a issue with standing waves - you wouldn't know where they are coming from , where as directional mics will.   

I would quote Darko… there isn’t bad audio gear, just mis-priced gear.  I like deep_333’s philosophy, an exceptional price requires exceptional novelty on the part of the designer / manufacturer.

My experience is loudspeakers sound like their defects.  Some of those defects we can see very clearly in measurements.  Some defects sound good in the short term and can fool us.  Some people like being fooled… others regret it.  For comb filtering-like responses certain notes will align with the comb peaks, others with the comb valleys, giving an impression of detail and excitement.

It seem likely this speaker will be very much a matter of taste and may require a lot of setup time to get it right for your listening space.

With speakers it is close to impossible to have a "flat line" speaker that will sound good in your room, So you get your "flat line" speaker home and it promises to disappoint. 

Not all dips are created equal even if they look similar. How the dip was caused makes a significant difference.

Comb filter effects tend to be considerably more benign than the dip in an anechoic or quasi-anechoic curve implies. This is because the energy is actually still there, and arrives after a reflection or two, and tends to perceptually fill in the dip. The ear/brain system does not process sound the same way that microphones do.

The floor bounce dip is a comb filter effect that looks dreadful on paper but is relatively benign because it is filled in by the subsequent room reflections. If you want to compare what the floor bounce dip sounds like with and without reflections, have someone talk to you from a few feet away indoors. Pay attention to the timbre of their voice. Then walk outdoors and have that person talk to you again from about the same distance, again paying attention to the timbre of their voice. The direct sound is the exact same; the reflections are what’s different. Without reflections filling in the floor-bounce dip, their voice sounds much thinner.

Another virtually ubiquitous comb filter effect is the 2 kHz stereo dip. At about 2 kHz the signal from the left speaker arrives at the right ear delayed by 1/2 wavelength (because of the path-length difference), and a comb-filter cancellation dip results. Likewise at the left ear the same thing happens. In approximately anechoic conditions (including near-field listening) this dip can be audible, and mixing engineers actually use this dip in their well-damped mixing rooms to find exactly where their ears should be when using nearfield monitors. But in a normal listening set-up, this comb filter effect is filled in by the in-room reflections and is not noticeable.

On the other hand, a dip that is due to reduced output from a driver is far more likely to be audible and objectionable because it shows up in the direct sound and in the reflections.

Microphone height can make a great deal of difference in the on-axis frequency response measurement depending on how directional the drivers are in the vertical plane and how their outputs are combining at the microphone location. In practice there is often considerably less change in timbre at the listening position than one might expect from the differing curves taken at different microphone heights because the in-room contribution of the reflections tends to average things out.

Don’t get me wrong, I am very much pro-measurements! The first 90 percent or so of my work on a design is purely measurement-based. But sometimes measurements taken at face value can be misleading; ime the actual cause of frequency response anomalies needs to be understood and taken into account. It takes a LOT of measurements to tell enough of the story to get a reliable picture of what’s going on, and even then the characteristics of the human hearing system can result in perception not precisely matching up with expectations.

Duke

I'm reading @audiokinesis but avoiding commenting when I just don't know what I'm talking about.  Honestly my experience with very poor measuring speakers is rather limited so I yield the floor. 🤣